Symptoms. The symptoms are generally well defined and well developed. The onset is sudden; an animal which one day before appeared perfectly well is attacked in one or several joints. Usually the upper joints of the limb are involved—the shoulder, elbow, knee, haunch, stifle, hock.
Nevertheless, invasion is probably not as sudden as it appears to be, and, as in the human species, the subject begins by feeling erratic pains, which, however, pass unnoticed. The animal moves with difficulty, as though it were suffering from laminitis, and has pain when placing weight on the limb, while the joint attacked soon shows a swelling which extends to the tendon sheaths and the neighbouring serous bursæ. The local temperature is higher than that of surrounding parts, sensibility becomes very marked, and pain attends the slightest pressure on, or even movement of, the affected joint. Intense lameness follows, which may even at first give rise to the suspicion of fracture. The animals remain lying for long periods, groan from time to time, and suffer great pain when rising.
In some cases the local manifestations appear to be transferred from one joint to another.
These local symptoms are accompanied by high fever. The temperature rises to 105° or 106° Fahr., the pulse to 80 or 90, and the breathing is enormously accelerated if the patients are forced to move.
Loss of appetite is very marked. Rumination may be suspended, and these grave symptoms are accompanied by constipation, rapid wasting, cessation or marked diminution of the milk supply, decrease in the quantity of urine passed, etc.
A few days after the onset, visceral complications may occur, though fortunately such complications are far from being constant. Auscultation and percussion sometimes reveal the lesions of pleurisy, endocarditis, pericarditis, etc.
The development of articular rheumatism varies greatly, and may occasionally continue for weeks or months, the condition of one joint improving only to be followed by inflammation of another.
The visceral lesions rarely disappear completely, and it is not uncommon to note symptoms of chronic valvular endocarditis. Relapses are somewhat frequent, and the disease may continue in a chronic form after the acute symptoms have disappeared.
Lesions. The joint itself is not alone affected. All the tissues surrounding it are congested, swollen and painful, particularly the sheaths and insertions of the tendons. Within the inflamed synovial capsules of the joints an increased quantity of turbid synovia accumulates, distending the joint and producing a condition of hydrarthrosis.
In animals slaughtered during the course of the disease one finds congestive infiltration of the limbs.